Translate the overscroll elasticity layer by the overscroll amount

cc/trees/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
@@ skipping 1249 matching lines @@
   transform->matrix().set(1, 3, MathUtil::Round(transform->matrix().get(1, 3)));
 }
 
 template <typename LayerType>
 struct SubtreeGlobals {
   LayerSorter* layer_sorter;
   int max_texture_size;
   float device_scale_factor;
   float page_scale_factor;
   const LayerType* page_scale_application_layer;
+  gfx::Vector2dF elastic_overscroll;
+  const LayerType* elastic_overscroll_application_layer;
   bool can_adjust_raster_scales;
   bool can_render_to_separate_surface;
   bool layers_always_allowed_lcd_text;
 };
 
 template<typename LayerType>
 struct DataForRecursion {
   // The accumulated sequence of transforms a layer will use to determine its
   // own draw transform.
   gfx::Transform parent_matrix;
@@ skipping 813 matching lines @@
       render_surface_layer_list->size();
   size_t layer_list_child_sorting_start_index = descendants.size();
 
   if (!layer->children().empty()) {
     if (layer == globals.page_scale_application_layer) {
       data_for_children.parent_matrix.Scale(
           globals.page_scale_factor,
           globals.page_scale_factor);
       data_for_children.in_subtree_of_page_scale_application_layer = true;
     }
+    if (layer == globals.elastic_overscroll_application_layer) {
+      data_for_children.parent_matrix.Translate(globals.elastic_overscroll.x(),
+                                                globals.elastic_overscroll.y());
+    }
 
     // Flatten to 2D if the layer doesn't preserve 3D.
     if (layer->should_flatten_transform())
       data_for_children.parent_matrix.FlattenTo2d();
 
     data_for_children.scroll_compensation_matrix =
         ComputeScrollCompensationMatrixForChildren(
             layer,
             data_from_ancestor.parent_matrix,
             data_from_ancestor.scroll_compensation_matrix,
@@ skipping 258 matching lines @@
   gfx::Transform scaled_device_transform = inputs.device_transform;
   scaled_device_transform.Scale(inputs.device_scale_factor,
                                 inputs.device_scale_factor);
 
   globals->layer_sorter = NULL;
   globals->max_texture_size = inputs.max_texture_size;
   globals->device_scale_factor =
       inputs.device_scale_factor * device_transform_scale;
   globals->page_scale_factor = inputs.page_scale_factor;
   globals->page_scale_application_layer = inputs.page_scale_application_layer;
+  globals->elastic_overscroll = inputs.elastic_overscroll;
+  globals->elastic_overscroll_application_layer =
+      inputs.elastic_overscroll_application_layer;
   globals->can_render_to_separate_surface =
       inputs.can_render_to_separate_surface;
   globals->can_adjust_raster_scales = inputs.can_adjust_raster_scales;
   globals->layers_always_allowed_lcd_text =
       inputs.layers_always_allowed_lcd_text;
 
   data_for_recursion->parent_matrix = scaled_device_transform;
   data_for_recursion->full_hierarchy_matrix = identity_matrix;
   data_for_recursion->scroll_compensation_matrix = identity_matrix;
   data_for_recursion->fixed_container = inputs.root_layer;
@@ skipping 58 matching lines @@
       inputs->current_render_surface_layer_list_id);
 
   // The dummy layer list should not have been used.
   DCHECK_EQ(0u, dummy_layer_list.size());
   // A root layer render_surface should always exist after
   // CalculateDrawProperties.
   DCHECK(inputs->root_layer->render_surface());
 }
 
 }  // namespace cc